No round-robin multipathing option, only failover with manual fallback.

We decided to make it work with DM-MP

Mirroring

As mentioned above, the mirroring will be made through mdadm.

The question was about the necessarity to use "fd Linux raid autodetect" partitions or not.

We first setup things using fd partitions, but after rebooting the servers, we faced an unsolvable problem.

As mdadm is started in the rc.sysinit before DM-MP on RHEL 4 (and 5), we ended up with md raid1 arrays built with /dev/sdX devices rather than /dev/dm devices.

Instead of hacking the rc.sysinit script, we removed the fd partitions and created a /etc/init.d/mdadm script that starts mdadm after dm-multipath is loaded. The raid1 arrays are setup in the /etc/mdadm.conf file.

No "fd Linux RAID autodetect" partitions.

Volume management

LVM2 is the tool used for volume management for its flexibility over pure partitions.

Detailled setup

Multipath

Our test server is dual FC connected to an HP EVA 8100 Array. Both Luns (VDISK) are from the same disk array, but the goal in production is to present to the server a Lun from 2 different disks arrays located on 2 different sites.